Language or behavior that simply assumes that a given person is heterosexual.

Discrimination against nonheterosexuals as it is institutionalized
in law and society. In this usage, heterosexism is often contrasted to
homophobia, the visceral fear or hatred of homosexuals,
which occurs in individuals.

When talking about marital status, remember that in most surveys/studies the "single" category generally includes people who
are in same-sex couples. When talking about couples, be clear whether
you're referring only to heterosexual relationships or not.

If you hear something that seems unintentionally heterosexist, point it out to the speaker/writer. In many cases, this is a simple oversight, and the person may be glad to be corrected.

If someone tells you that you've said or done something heterosexist, don't feel offended or accused of being a bad person. Heterosexism is so pervasive that everyone is guilty of it once in a while, straight or not.

In general, don't assume that everyone is straight. Discourage
others from assuming everyone is straight.

Tips adapted from "isms at a University Community, a Workshop" held at Slippery Rock University, 1993.